Refrigerator

ABSTRACT

It is an object of the present invention to provide a refrigerator which is able to improve the efficiency of the refrigerating cycle while avoiding causing the structure of the refrigerator to be complicated, and avoiding a cost increase. Refrigerator  30  includes a refrigerating cycle device  20  having a compressor  1 , a radiator  2  connected to a discharge side of the compressor  1 , a first expansion valve  31  connected to an exit side of the radiator  2 , a gas-liquid separator  33  for separating a refrigerant, which is in a mixed gas-liquid state by being decompressed by the first expansion valve  31 , into a gas refrigerant and a liquid refrigerant, a heat absorber  14  into which the liquid refrigerant discharged from the gas-liquid separator  33  flows, and a refrigerant pipe  6 D for delivering the gas refrigerant discharged from the gas-liquid separator  33  into the middle pressure portion of the compressor  1 ; an outer case  40 ; an inner case  39 ; and a heat insulating material. The gas-liquid separator  33  is arranged in the heat insulating material  47.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a refrigerator, and in particular, it relatesto an improvement of cooling capacity and efficiency in a refrigerator.

2. Description of the Related Art

In recent years, due to problems such as global warming, there has beena growing demand for the reduction of environmental burdens, and thelike, and because of this, a large number of techniques have beenproposed for the purpose of reducing electric power consumption andimprovement of efficiency in cooling operation for a refrigerator.

For example, Japanese Unexamined Patent Publication No. H11-148761discloses a technique for improving the efficiency of an operation in arefrigerator by cooling a refrigerating compartment and a freezingcompartment alternately and repeatedly to reduce the compression ratioof a compressor.

Furthermore, for the purpose of providing an energy-saving freezingrefrigerator by improving efficiency of the refrigerating cycle whilecooling a freezing compatment, Japanese Unexamined Patent PublicationNo. 2004-32492 discloses a technique for improving efficiency of therefrigerating cycle by lowering the condensation temperature of therefrigerating cycle by means of a condenser in the refrigeratingcompartment, and by conducting a freezing cycle operation for thefreezing compartment with a low compression ratio.

However, in the aforementioned conventional structure, there is a limiton further improving the efficiency of the refrigerating cycle, and alsothere is a possibility of causing an increase in cost due to thecomplicated structure and control of the refrigerator.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide arefrigerator which is able to improve the efficiency of therefrigerating cycle while avoiding causing the structure of therefrigerator to be complicated, and avoiding a cost increase.

In a first aspect of the present invention, there is provided arefrigerator comprising a refrigerating cycle device including acompressor having a middle pressure portion, a radiator connected to adischarge side of the compressor, first decompression means connected toan exit side of the radiator, gas-liquid separation means for separatinga refrigerant, which is in a mixed gas-liquid state by beingdecompressed by the first decompression means, into a gas refrigerantand a liquid refrigerant, second decompression means into which theliquid refrigerant discharged from the gas-liquid separation meansflows, a heat absorber into which the refrigerant discharged from thesecond decompression means flows, and a refrigerant pipe for deliveringthe gas refrigerant discharged from the gas-liquid separation means tothe middle pressure portion; an outer case; an inner case; and a heatinsulating material for filling a gap between the outer case and theinner case; wherein; the gas-liquid separation means is arranged in theheat insulating material.

According to the aforementioned structure, the refrigerator providedwith the gas-liquid separation means has no need to provide a specialheat insulating material for the gas-liquid separator except providing aheat insulating material for the main body of the refrigerator, andthereby low cost is achieved, and also dew condensation and atemperature rise can be avoided.

In a second aspect of the present invention, there is provided arefrigerator comprising a refrigerating cycle device, including acompressor having a middle pressure portion, a radiator connected to adischarge side of the compressor, first decompression means connected toan exit side of the radiator, gas-liquid separation means for separatinga refrigerant, which is in a mixed gas-liquid state by beingdecompressed by the first decompression means, into a gas refrigerantand a liquid refrigerant, second decompression means into which theliquid refrigerant discharged from the gas-liquid separation meansflows, a heat absorber into which the refrigerant discharged from thesecond decompression means flows, and a refrigerant pipe for deliveringthe gas refrigerant discharged from the gas-liquid separation means tothe middle pressure portion; an outer case; an inner case; and a storagebox filled with heat insulating material; wherein the gas-liquidseparation means is housed in the storage box.

According to the aforementioned structure, the refrigerator providedwith the gas-liquid separation means has no need of providing a specialheat insulating material for the gas-liquid separator except providing aheat insulating material for the main body of the refrigerator, andthereby low cost is achieved, and additionally dew condensation and atemperature rise can be avoided. Also, maintainability of weldedportions of the gas-liquid separation means, and the like, can beimproved.

In a third aspect of the present invention, in the refrigerator of thefirst or the second aspect, the refrigerator includes a refrigeratingcompartment, and a freezing compartment in which a temperature ismaintained lower than a temperature of the refrigerating compartment,and the gas-liquid separation means is placed closer to therefrigerating compartment than to the freezing compartment.

According to the aforementioned structure, the refrigerator providedwith the gas-liquid separation means avoids heat leakage from thegas-liquid separation means to the freezing compartment.

In a fourth aspect of the present invention, the refrigerator of any oneof first aspect to the third aspect includes a heat exchanger arrangedto be capable of conducting heat exchange between the refrigerant whichis between the discharge side of the compressor and the firstdecompression means, and the refrigerant which is between an exit sideof the heat absorber and a suction port of the compressor.

In a fifth aspect of the present invention, the refrigerator of any oneof first aspect to the fourth aspect includes a first heat exchangerarranged to be capable of conducting heat exchange between the liquidrefrigerant which is separated by the gas-liquid separation means beforeentering the second decompression means, and the refrigerant which is inbetween the exit side of the heat absorber and the suction port of thecompressor, and/or a second heat exchanger arranged to be capable ofconducting heat exchange between the refrigerant which is between thedischarge side of the compressor and the first decompression means, andthe gas refrigerant which is separated by the gas-liquid separationmeans before being delivered into the middle pressure portion of thecompressor.

According to the aforementioned structure, it is possible to supercoolthe refrigerant before entering the heat absorber, and thereby thecooling ability of the refrigerator is improved.

In a sixth aspect of the present invention, there is provided arefrigerator comprising a refrigerating cycle device which includes acompressor, a radiator connected to a discharge side of the compressor,decompression means connected to an exit side of the radiator, and aheat absorber into which a liquid refrigerant discharged from thedecompression means flows, and which is filled with a carbon dioxiderefrigerant; an outer case; an inner case; and heat insulating materialfor filling a gap between the outer case and the inner case; wherein ahigh pressure refrigerant pipe extending from the radiator is embeddedin the heat insulating material.

According to the aforementioned structure, in the case where therefrigerator uses carbon dioxide as a refrigerant, the high pressureside is operated near the supercritical pressure, and therefore, whenthe high pressure refrigerant pipe is cooled in the heat insulatingmaterial, it is possible to obtain higher supercooling effect than thecase in which a CFC-type refrigerant or hydrocarbon refrigerant is used,and thus the cooling ability of the refrigerator can be improved.Furthermore, since the high pressure side of the refrigerating cycle iscooled, the high pressure of the refrigerating cycle can be decreasedand the compression efficiency of the compressor can be improved.

In a seventh aspect of the present invention, in the refrigerator of thesixth aspect, a second heat insulating material which has lower thermalconductivity than the heat insulating material is provided in the heatinsulating material arranged in a back of the refrigerator; and the highpressure refrigerant pipe is placed outside a side edge of the secondheat insulating material.

According to the aforementioned structure, it is possible to effectivelycool the high pressure refrigerant pipe of the refrigerating cycle byusing cold energy leaking outside by surrounding the second heatinsulating material which has lower thermal conductivity, such as vacuumheat insulating material.

The present invention provides a refrigerator capable of improving theefficiency of a refrigerating cycle while avoiding causing the structureof refrigerator to be complicated, and avoiding a cost increase.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are views showing an outline structure of a preferredembodiment of a refrigerator according the present invention;

FIG. 2 is a view showing an enthalpy-pressure chart of a refrigeratingcycle during a freezing operation of the embodiment of the refrigeratoraccording the present invention;

FIG. 3 is a view showing an enthalpy-pressure chart of a refrigeratingcycle during a refrigerating operation of the embodiment of therefrigerator according the present invention;

FIG. 4 is a view showing an outline structure of a refrigeratoraccording to a second embodiment of the present invention;

FIG. 5 is a view showing an outline structure of a refrigeratoraccording to a third embodiment of the present invention; and

FIG. 6 is a view showing an outline structure of a refrigeratoraccording to a forth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the refrigerator of the present invention willbe explained hereinbelow with reference to the accompanying drawings.

First Embodiment

An embodiment of the present invention is described in detail withreference to the accompanying drawings. FIGS. 1A to 1C are viewsillustrating an outline structure of a refrigerator 30 according to thepresent embodiment, wherein FIG. 1A is a side sectional view of therefrigerator 30 according to the present invention, FIG. 1B is a rearelevation of the refrigerator 30, and FIG. 1C is a sectional view, takenalong the line Z-Z in FIG. 1B.

As shown in FIG. 1A, the refrigerator 30 includes a refrigerating cycleunit 20, an outer case 40, an inner case 39, doors 62 and 63, and amiddle partition wall 50. A refrigerating compartment 41 and a freezingcompartment 42 are formed by partitioning the inner case 39 by using thedoors 62 and 63 and the middle partition wall 50.

The refrigerating cycle unit 20 includes a compressor 1; a radiator 2connected to the discharge side of the compressor 1; a first expansionvalve 31 as decompression means provided in a refrigerant pipe 6A on theexit side of the radiator 2; a gas-liquid separator 33 as gas-liquidseparation means connected to the exit side of the first expansion valve31; a second expansion valve 32 as decompression means provided in arefrigerant pipe 6C which is on the exit side of the gas-liquidseparator 33 and from which a liquid refrigerant separated by thegas-liquid separator flows; a heat absorber 14 which is as a heatexchanger for cooling respective compartments 41 and 42 and which isconnected to the exit side of the second expansion valve 32; and a firstheat exchanger 65 capable of conducting heat exchange between therefrigerant from the radiator 2 and the refrigerant from the heatabsorber 14. Also, the refrigerating cycle is formed by connecting arefrigerant pipe 6B on the exit side of the heat absorber 14 to thesuction port of the compressor 1, and by connecting the upper portion ofthe gas-liquid separator 33 to a middle pressure portion of thecompressor 1 via a refrigerant pipe 6D.

Incidentally, the gas refrigerant separated by the gas-liquid separator33 is returned to the middle pressure portion of the compressor 1through the refrigerant pipe 6D.

Furthermore, the first expansion valve 31 and the second expansion valve32 are constructed so that the degree of throttling can be changed. Itis possible to change the separation efficiency in the gas-liquidseparator 33 by changing the degree of throttling in the first expansionvalve 31 so that the pressure of the refrigerant is reduced to apredetermined pressure and the gas refrigerant is generated until therefrigerant reaches the gas-liquid separator 33, and thus therefrigerant flows into the gas-liquid separator 33 in a mixed gas-liquidstate (a two-phase mixture of gas/liquid). On the other hand, it ispossible to control the evaporation temperature of the refrigerant inthe heat absorber 14 by changing the degree of throttling in the secondexpansion valve 32 so that the pressure of the refrigerant is reduced toa predetermined level until the refrigerant reaches the heat absorber14.

The compressor 1 is a two-stage compressor which includes a first stagecompression portion 1A and a second stage compression portion 1B insidea sealed container. The compressor 1 also includes a middle cooler 1C,which is provided on a refrigerant pipe outside the sealed container,and which connects the first stage compression portion 1A and the secondstage compression portion 1B. Furthermore, the refrigerant pipe 6D isconnected to be able to deliver the gas refrigerant to the middlepressure portion of the compressor 1, that is, between the middle cooler1C and the second stage compression portion 1B. Incidentally, the gasrefrigerant from the gas-liquid separator 33 is delivered to the middlepressure portion of the compressor 1 due to a pressure difference insidethe refrigerant pipe 6D. The compressor 1 is not limited to a two-stagecompressor. For example, if a one-stage compressor is employed, therefrigerant pipe 6D may be connected to the middle pressure portion ofthe one-stage compressor. Also, even if a structure in which a pluralityof compressors are connected is used, the refrigerant pipe 6D can beformed to be connected to a middle pressure portion between a compressorof a lower stage side and a compressor of a higher stage side.

In FIG. 1A, the path from the discharge side of the second stagecompression portion 1B to the entrance of the first expansion valve 31via the radiator 2 is operated as a high pressure portion of therefrigerating cycle. Also, the path from the discharge side of the firststage compression portion 1A to the suction port of the second stagecompression portion 1B via the middle cooler 1C, the path from the exitof the first expansion valve 31 to the entrance of the second expansionvalve. 32 via the gas-liquid separator 33, and the path of therefrigerant pipe 6D are operated as middle pressure portion of therefrigerating cycle. Furthermore, the path from the exit of the secondexpansion valve 32 to the suction port of the first stage compressionportion 1A via the heat absorber 14 is operated as a low pressureportion of the refrigerating cycle.

The gap formed between the outer case 40 and the inner case 39, andbetween the inner member and the outer member of the doors 62 and 63,and the like, is filled with a heat insulating material 47. Polyurethanefoam is used as the heat insulating material 47, and the gap can befilled with the heat insulating material 47 by injecting concentratedsolution of the polyurethane foam and by foaming the same.

Furthermore, in the refrigerator 30 of the present embodiment, as shownin FIGS. 1A to 1C, a vacuum heat insulating material 61 is provided onthe back of the refrigerator 30 between the heat insulating material 47and the outer case 40, with a predetermined distance of, for example, 50to 150 mm from the top, bottom, left, and right edge portion of theouter case 40. The vacuum heat insulating material 61 is constructed byhousing a core material such as micronized powder of glass fiber,silica, pearlite, and the like, silica aerogel, or open-cellpolyurethane foam inside an air non-permeable outer body, and byextracting air from the inside, and thus, for a single panel vacuum heatinsulating material, the vacuum heat insulating material 61 providesexcellent thermal insulating ability with a thermal conductivity ofabout 0.002 to 0.005 W/m.K. Incidentally, the thermal conductivity ofthe polyurethane form used as the heat insulating material 47 is about0.022 W/m.K.

In this instance, as shown in FIGS. 1B and 1C, among the high pressureportions of the refrigerating cycle, the refrigerant pipe 6A extendingfrom the radiator 2 is placed outside the side edge of the vacuum heatinsulating material 61. This is to cool the refrigerant pipe 6Aeffectively by using cold energy which escapes from the compartments 41nad 42 to the outside avoiding the vacuum heat insulating material 61,since the vacuum heat insulating material 61 has a very low thermalconductivity and high thermal insulating ability, and is placed in theheat insulating material 47 in the preferred embodiment of the presentinvention, so the cold energy from respective compartments 41 and 42moves in the direction of dotted line arrows shown in FIG. 1C.

Furthermore, the refrigerator 30 has the refrigerating compartment 41 inthe upper part and the freezing compartment 42 in the lower part, andadditionally, an inner partition wall 43 is provided in the rear portionin the freezing compartment 42, and the heat absorber 14 is placedinside an air path 44 formed by the inner partition wall 43.

A first switching damper 45 is provided in the entrance A of the airpath 44, the first switching damper 45 being constructed so that it canbe switched between a closed position (the position of the dotted line)and an open position (the position of the solid line). Furthermore, afan 48 and a second switching damper 49 are provided in the exit B ofthe air path 44, the second switch damper 49 being constructed so thatit can be switched between a closed position (the position of the dottedline) and an open position (the position of the solid line). When thesecond switching damper 49 is in the position of the solid line, an openportion 51 of the middle partition wall 50 is closed by the secondswitching damper 49.

Furthermore, a back air path 46 is provided in the heat insulatingmaterial 47 on the back of the refrigerator 30. Thereby, when both thefirst switching damper 45 and the second switching damper 49 areswitched to the positions of the dotted lines, the air path 44 and therefrigerating compartment 41 are in communication via the back air path46. On the other hand, when both the first switching damper 45 and thesecond switching damper 49 are switched to the positions of the solidlines, the air flow through the back air path 46 is blocked, and the airpath 44 and the freezing compartment 42 are in communication.

In the refrigerating cycle device 20 of the refrigerator 30 according tothe present embodiment, taking account of combustibility, toxicity, andthe like, carbon dioxide (CO2) refrigerant, which is a naturalrefrigerant and imposes less burdens on the environment, is used as therefrigerant. Additionally, mineral oil, alkyl benzene oil, etheral oil,PAG (polyalkylene glycol), POE (polyol ester), and the like, are used asoil for lubricant of the compressor 1.

Thus, as the refrigerator 30 uses carbon dioxide as a refrigerant, forexample, if the outside air temperature becomes more than the criticaltemperature (about +31° C.) for carbon dioxide, the high pressureportion of the refrigerating cycle enters a supercritical condition, andthereby the refrigerating cycle of the refrigerator 30 is operated as atrans-critical cycle.

The operation of the refrigerator 30 having the aforementioned structureis explained with reference to FIGS. 1A-1C and 2. FIG. 2 is anenthalpy-pressure (p-h) chart of the refrigerating cycle during thefreezing operation in the refrigerator 30 of the present embodiment andFIG. 3 is an enthalpy-pressure (p-h) chart of the refrigerating cycleduring refrigerating operation in the refrigerator 30. In FIGS. 2 and 3,the cycle line shown with the solid line is the cycle line of therefrigerator 30 of the present embodiment.

Incidentally, unlike the refrigerator 30 of the present embodiment, thecycle line shown with the dotted line in FIG. 2 is a cycle line of acomparative example of a refrigerator in which the refrigerant pipe 6Aon the exit side of the radiator 2 is not embedded in the heatinsulating material 47. The comparison is described in detail later.

The refrigerator 30 is selectively operated by the control device (notshown) between a freezing operation (for example, around −26° C.) forcooling the freezing compartment 42, and a refrigerating operation (forexample, around −5° C.) for cooling the refrigerating compartment 41. Ineach operation, the first expansion valve 31 and the second expansionvalve 32 are controlled by the control device (not shown) to have apredetermined degree of openness.

Furthermore, during the freezing operation, by placing the firstswitching damper 45 in the position for opening the entrance A of theair path 44 (the solid line), and the second switching damper 49 in theposition for opening the exit B of the air path 44 (the solid line), theair inside the freezing compartment 42 is circulated and cooled by theheat absorber 14. Furthermore, during the refrigerating operation, byplacing the first switching damper 45 in the position for closing theentrance A of the air path 44 (the dotted line), and the secondswitching damper 49 in the position for closing the exit B of the airpath 44 (the dotted line), the air inside the refrigerating compartment41 is circulated via the back air path 46 and cooled by the heatabsorber 14.

First, the freezing operation is explained by using the cycle line shownwith the solid line in FIG. 2. In the present embodiment, when thecompressor 1 is operated, the refrigerant discharged from the compressor1 is cooled by the radiator 2 to radiate the heat. That is, first, therefrigerant flows in the following order: (1) the suction port of thefirst stage compression portion 1A; (2) the discharge port of the firststage compression portion 1A; (3) the suction port of the second stepcompression portion 1B; and (4) the discharge port of the second stagecompression portion 1B. Continuously, the refrigerant flows in thefollowing order: (5) the exit of the radiator 2 and also the entrance ofthe first heat exchanger 65; (9) the exit of the first heat exchanger65; (10) the entrance of the expansion valve 31; and (6) the exit of thefirst expansion valve 31. In this situation, the refrigerant is in thetwo-phase mixture of gas/liquid.

In this situation, the proportion of gas to liquid is equivalent of theproportion of the length of a line segment L1 (gas) to the length of aline segment L2 (liquid). The refrigerant enters the gas-liquidseparator 33 in the state of the two-phase mixture of gas/liquid. Thegas refrigerant, which has been separated in this point, is delivered tothe middle pressure portion of the compressor 1 through the refrigerantpipe 6D, that is, led to a portion between the middle cooler 1C and thesecond stage compression portion 1B. Character (13) designates the exitof the gas/liquid separator 33 (gas refrigerant), and the refrigerantwhich has passed this point reaches the suction port of the second stagecompression portion 1B (3), and then the refrigerant is compressed inthe second stage compression portion 1B.

On the other hand, the liquid refrigerant, which has been separated bythe gas-liquid separator 33, flows through the refrigerant pipe 6C, andreaches the second expansion valve 32. Character (7) designates theentrance of the second expansion valve 32, character (8) is the exit ofthe second expansion valve 32, and character (12) is the exit of theheat absorber 14. After the liquid refrigerant flown into the heatabsorber 14 evaporates and absorbs the heat of the air inside the airpath 44, and the liquid refrigerant conducts heat exchange with therefrigerant coming from the radiator 2 in the first heat exchanger 65,and returns to the suction portion of the first stage compressionportion 1A. Character (13) is the exit of the first heat exchanger 65.

During the freezing operation, the refrigerating cycle is operated asdescribed above, and also the first switching damper 45 is placed in theposition for opening the entrance A of the air path 44 (the solid line)and the second switching damper 49 is placed in the position for openingthe exit B of the air path 44 (the solid line), and therefore, the airinside the freezing compartment 42 is circulated by the fan 48, and thusthe circulated air is cooled by the heat absorber 14, resulting incooling the freezing compartment 42.

On the contrary, during the refrigerating operation, the cycle lineshown with the olid lines in FIG. 3 is formed. During the refrigeratingoperation too, when the compressor 1 is operated, the refrigerantdischarged from the compressor 1 is also cooled by the radiator 2 toradiate the heat. That is, first, the refrigerant flows in the followingorder: (41) the suction port of the first step compression portion 1A;(42) the discharge port of the first stage compression portion 1A; (43)the suction port of the second stage compression portion 1B; and (44)the discharge port of the second stage compression portion 1B.Continuously, the refrigerant flows in the following order: (45) theexit of the radiator 2 and also the entrance of the first heat exchanger65; (49) the exit of the first heat exchanger 65; (60) the entrance ofthe expansion valve 31; and (46) the exit of the first expansion valve31. In this situation, the refrigerant is in the two-phase mixture ofgas/liquid.

In this situation, the proportion of gas to liquid is equivalent of theproportion of the length of a line segment L1 (gas) to the length of aline segment L2 (liquid). The refrigerant enters the gas-liquidseparator 33 in the state of the two-phase mixture of gas/liquid. Thegas refrigerant, which has been separated in this point, is delivered tothe middle pressure portion of the compressor 1 through the refrigerantpipe 6D, that is, led to a portion between the middle cooler 1C and thesecond stage compression portion 1B. The reference numeral (53)designates the exit of the gas/liquid separator 33 (gas refrigerant),and the refrigerant which has passed this point reaches (43) the suctionport of the second step compression portion 1B, and then the refrigerantis compressed in the second stage compression portion 1B.

On the other hand, the liquid refrigerant, which has been separated bythe gas-liquid separator 33, flows through the refrigerant pipe 6C, andreaches the second expansion valve 32. Character (47) designates theentrance of the second expansion valve 32, character (48) is the exit ofthe second expansion valve 32, and character (62) is the exit of theheat absorber 14. After the liquid refrigerant flown into the heatabsorber 14 evaporates and absorbs the heat of the air inside the airpath 44, the liquid refrigerant conducts heat exchange with therefrigerant coming from the radiator 2 in the first heat exchanger 65,and returns to the suction portion of the first stage compressionportion 1A. Character (63) is the exit of the first heat exchanger 65.

As described above, during the refrigerating operation, therefrigerating cycle is performed in almost the same way as theaforementioned freezing operation, except that evaporation temperature,middle pressure, and the like, increase. Here, the arrangement is suchthat during the refrigerating operation, since the first switchingdamper 45 is placed in the position for closing the entrance A of theair path 44 (the dotted line) and the second switching damper 49 isplaced in the position for closing the exit B of the air path 44 (thedotted line), the inside air flows through the back air path 46, so theair in the refrigerating compartment 41 is circulated by the fan 48through the air path 44 and the back air path 46, and the circulated airis cooled by the heat absorber 14, resulting in cooling therefrigerating compartment 41.

The refrigerant is circulated and the state changes, so therefrigerating cycle is formed, during both the freezing operation andthe refrigerating operation, as described above, whereby the respectivecompartments 41 and 42 are cooled to maintain a predeterminedtemperature, respectively.

Since carbon dioxide is used as a refrigerant for the refrigeratingcycle device 20 of the present embodiment, even if atmospherictemperature (outside air temperature) around the radiator 2, that is,the temperature of the exit of the radiator 2 of (5) in FIG. 2 is, forexample, 26° C., as shown in the figure, it is difficult to obtainsufficient cooling ability in the heat absorber 14 because the drynessof the refrigerant flowing into the second expansion valve 32 is toohigh and the proportion of the gas refrigerant in the refrigerant ishigh, compared to the case in which the conventional CFC-typerefrigerant or HC-type refrigerant is used.

Therefore, in the refrigerator 30 of the present embodiment, thearrangement is such that the refrigerant from the radiator 2 can becooled in the first heat exchanger 65, and furthermore, the refrigerantfrom the radiator 2 can be further cooled by embedding all or a portionof the refrigerant pipe 6A, preferably 60% or more of the length of therefrigerant pipe 6A, in the heat insulating material 47. Thereby, in therefrigerator 30, the supercooling degree of the refrigerator afterdischarged from the radiator 2 and before entering the heat absorber 14can be increased, and a drastic improvement of the cooling ability canbe expected. Incidentally, since the inside of the heat insulatingmaterial 47 has an intermediate temperature between the ambienttemperature and the inside temperature of the refrigerator, therefrigerant from the radiator 2 can be cooled by the heat insulatingmaterial 47.

As described above, the portion from (5) to (9) in the cycle line shownwith the solid line is the cooling by the first heat exchanger 65, andthe portion from (9) to (10) in the same cycle line is the cooling bythe heat insulating material 47. Thereby, in the refrigerator 30 of thepresent embodiment, it is possible to obtain sufficient cooling abilityeven if carbon dioxide is used as the refrigerant.

Here, the case in which the refrigerant pipe 6A is not embedded in theheat insulating material 47 is explained as a comparative example. Inthis case, the cycle line shown with the dotted line in FIG. 2 is formedduring the freezing operation. Characters (1), (2), and the like in thecycle line shown with the dotted line show the same states as thoseshown by the same characters in the cycle line with the aforementionedsolid line, in the refrigerating cycle,

In FIG. 2, in the comparison of the cycle line (solid line) of thepresent embodiment with the cycle line (dotted line) of the comparativeexample, in the cycle line with the solid line, the cooling effect ofthe heat insulating material 47 is shown, in the portion from (9) to(10), whereas in the cycle line with the dotted line, no cooling effectby the heat insulating material 47 is shown, and therefore, there is adifference in which the reference numeral (9) becomes the exit of thefirst heat exchanger 65 and the entrance of the first expansion valve31.

Thereby, in the cycle line (solid line) of the present embodiment, thecooling ability in the heat absorber 14 is enhanced, and also the highpressure of the refrigerating cycle is decreased and thus thecompression work of the compressor 1 decreases.

Incidentally, when carbon dioxide is used as a refrigerant, as in therefrigerator 30 of the present embodiment, the cooling effect of theaforementioned heat insulating material 47 is more remarkable, comparedto the case in which a conventional refrigerant is used. This isbecause, when carbon dioxide is used as a refrigerant, since therefrigerating cycle is often operated near the supercritical pressure,the effect of decreasing the high pressure of the refrigerating cycle islarger than the effect obtained in a conventional refrigerant.

Furthermore, even though the cooling effect of the heat insulatingmaterial 47 can be obtained not only during the freezing operation asdescribed above but also during the refrigerating operation, but thecooling effect during the refrigerating operation is almost the same asthat during the freezing operation, and the explanation thereof isomitted.

Furthermore, in the present embodiment, as described above, since therefrigerant pipe 6A is allocated outside the side edge of the vacuumheat insulating material 61, it is possible to cool the refrigerant pipe6A by effectively using the leakage of cold energy escaping fromrespective compartments 41 and 42 in the direction of dotted line arrowsshown in FIG. 1C.

Furthermore, in the present embodiment, since the gas-liquid separator33 is provided to deliver the gas refrigerant separated by thegas-liquid separator 33 to the middle pressure portion of the compressor1, that is, a portion between the middle cooler 1C and the second stagecompression portion 1B, the efficiency of the refrigerating cycle can beimproved. In particular, since the refrigerator 30 uses carbon dioxideas the refrigerant, with regard to the proportion of the gas to theliquid separated by the gas-liquid separator 33, the proportion of thegas (line segment L1) increases compared to the conventional CFC-typerefrigerant, so that the increased gas is delivered to the middlepressure portion of the compressor 1 and thereby the efficiency can beimproved.

Incidentally, as described above, the gas-liquid separator 33 isprovided in the present embodiment, and the gas-liquid separator 33 hasalmost the same temperature as the refrigerating compartment 42.Therefore, usually, it is necessary to perform a heat insulating processto avoid dew condensation and a temperature rise. However, in thepresent embodiment, since the gas-liquid separator 33 is embedded in theheat insulating material 47, a special heat insulating process is notneeded.

Furthermore, since the gas-liquid separator 33 has larger heat releasecompared to the refrigerant pipes, and the like, even if the gas-liquidseparator 33 is embedded in the heat insulating material, heat leakageoccurs to the freezing compartment 42 operated at a low temperature,depending on which portion in the heat insulating material 47 thegas-liquid separator 33 is embedded, and may result in a temperaturerise of the freezing compartment 42. However, since the gas-liquidseparator 33 of the present embodiment is allocated in the heatinsulating material 47 in the back of the refrigerating compartment 41,which is operated with a higher temperature than the freezingcompartment 42, the heat leakage can be suppressed.

Second Embodiment

Next, a second embodiment of the present invention is explained withreference to FIG. 4. FIG. 4 is a side sectional view of a refrigerator70 of the second embodiment. Incidentally, in FIG. 4, elements whichhave the same reference numerals as those of the elements in therefrigerator 30 of the first embodiment described above have the same orsimilar functions and effects as in the first embodiment. When comparedto the refrigerator 30 of the first embodiment described above, therefrigerator 70 has a difference in the point in which the refrigerator70 has a refrigerating cycle device 21 which includes a second heatexchanger 66 instead of the first heat exchanger 65.

The second heat exchanger 66 is able to conduct heat exchange betweenthe liquid refrigerant separated by the gas-liquid separator 33 and therefrigerant discharged from the heat absorber 14. That is, the secondheat exchanger 66 is formed between the refrigerant pipe 6C and therefrigerant pipe 6B. By using the second heat exchanger 66, the liquidrefrigerant before entering the second expansion valve 32 and the heatabsorber 14 can be effectively supercooled, and thus the cooling abilityby the heat absorber 14 can be improved as well as the efficiency of therefrigerating cycle can be also improved.

Third Embodiment

Next, a third embodiment of the present invention is explained withreference to FIG. 5. FIG. 5 is a side sectional view of a refrigerator90 of the third embodiment. Incidentally, in FIG. 5, elements which havethe same reference numerals as those in each embodiment described abovehave the same or similar functions and effects as in the firstembodiment. When compared to the refrigerator 70 of the secondembodiment described above, the refrigerator 90 has a difference in thepoint in which the refrigerator 90 has a refrigerating cycle device 22which includes a third heat exchanger 67 in addition to the second heatexchanger 66.

The third heat exchanger 67 is able to conduct heat exchange between therefrigerant discharged from the radiator 2 and the gas refrigerantseparated by the gas-liquid separator 33. That is, the third heatexchanger 67 is formed between the refrigerant pipe 6A and therefrigerant pipe 6D. By using the third heat exchanger 67, in additionto the supercooling effect of the second heat exchanger 66 of the secondembodiment described above, it is possible to cool the refrigerantdischarged from the radiator 2 before entering the gas-liquid separator33 by the gas refrigerant separated by the gas-liquid separator 33, andthus further improvement of the efficiency of the freezing cycle in therefrigerator 90 can be achieved.

Fourth Embodiment

Next, a fourth embodiment of the present invention is explained withreference to FIG. 6. FIG. 6 is a side sectional view of a refrigerator110 of the forth embodiment. Incidentally, in FIG. 6, elements whichhave the same reference numerals as those in each embodiment describedabove have the same or similar functions and effects as in the firstembodiment. Compared to the refrigerator 30 of the first embodimentdescribed above, the refrigerator 110 has a difference in a point inwhich the refrigerator 110 has a storage box 38.

The storage box 38 is provided in the back portion of the refrigeratingcompartment 41, and is a box-type storage portion detachably attached tothe inner case 39, and as shown in FIG. 6, the gas-liquid separator 33and the first expansion valve 31 are housed in the storage box 38.Incidentally, the inside of the storage box 38 is filled with heatinsulating material 47.

As described above, since the refrigerator 110 has a structure in whichthe gas-liquid separator 33 with a number of welded portions is housedinside the storage box 38 detachable from the inner case 39, even ifleakage of the refrigerant occurs from the welded portions of thegas-liquid separator 33, unlike the refrigerators of the aforementionedembodiments, it is not necessary to dismount the outer case 40 and theinner case 39 for conducting maintenance, but only necessary to dismountthe storage box 38, and therefore maintainability of the refrigerator110 improves.

Embodiments of the present invention are described above, however, thepresent invention is not limited to the above embodiments, but can bevariously modified.

In the embodiments of the present invention, the first expansion valve31 and the second expansion valve 32 are used as decompression means,however, the decompression means is not limited to this, and a capillarytube, or the like, can also be used. Furthermore, the gas-liquidseparator 33 is used as a gas-liquid separation means, however, thegas-liquid separation means is not limited to this, and any means whichis able to separate gas and liquid is acceptable. For example, aT-shaped refrigerant pipe which is inclined by 90 degrees can be used.

Furthermore, the refrigerator of the present invention may have all ofthe aforementioned heat exchangers, or one or two of the aforementionedheat exchangers, that is, the first heat exchanger 65, the second heatexchanger 66, and the third heat exchanger 67.

Materials for the heat insulating material 47 and the vacuum heatinsulating material 61 are not limited to those explained in theaforementioned embodiments, so far as the present invention can beappropriately constructed.

1. A refrigerator, comprising; a refrigerating cycle device including acompressor having a middle pressure portion, a radiator connected to adischarge side of the compressor, first decompression means connected toan exit side of the radiator, gas-liquid separation means for separatinga refrigerant, which is in a mixed gas-liquid state by beingdecompressed by the first decompression means, into a gas refrigerantand a liquid refrigerant, second decompression means into which theliquid refrigerant discharged from the gas-liquid separation meansflows, a heat absorber into which the refrigerant discharged from thesecond decompression means flows, and a refrigerant pipe for deliveringthe gas refrigerant discharged from the gas-liquid separation means tothe middle pressure portion; an outer case; an inner case; and a heatinsulating material for filling a gap between the outer case and theinner case; wherein the gas-liquid separation means is arranged in theheat insulating material.
 2. A refrigerator, comprising; a refrigeratingcycle device, including a compressor having a middle pressure portion, aradiator connected to a discharge side of the compressor, firstdecompression means connected to an exit side of the radiator,gas-liquid separation means for separating a refrigerant, which is in amixed gas-liquid state by being decompressed by the first decompressionmeans, into a gas refrigerant and a liquid refrigerant, seconddecompression means into which the liquid refrigerant discharged fromthe gas-liquid separation means flows, a heat absorber into which therefrigerant discharged from the second decompression means flows, and arefrigerant pipe for delivering the gas refrigerant discharged from thegas-liquid separation means to the middle pressure portion; an outercase; an inner case; and a storage box filled with a heat insulatingmaterial; wherein the gas-liquid separation means is housed in thestorage box.
 3. The refrigerator according to claim 1 or 2, furthercomprising a refrigerating compartment, and a freezing compartment inwhich the temperature is maintained lower than the temperature of therefrigerating compartment, and wherein the gas-liquid separation meansis placed closer to the refrigerating compartment than to the freezingcompartment.
 4. The refrigerator according to any one of claims 1 to 3,further comprising a heat exchanger arranged to be capable of conductingheat exchange between the refrigerant which is between the dischargeside of the compressor and the first decompression means, and therefrigerant which is between an exit side of the heat absorber and asuction port of the compressor.
 5. The refrigerator according to any oneof claims 1 to 4, further comprising: a first heat exchanger arranged tobe capable of conducting heat exchange between the liquid refrigerantwhich is separated by the gas-liquid separation means before enteringthe second decompression means, and the refrigerant which is between theexit side of the heat absorber and the suction port of the compressor,and/or a second heat exchanger which is capable of conducting heatexchange between the refrigerant which is between the discharge side ofthe compressor and the first decompression means, and the gasrefrigerant which is separated by the gas-liquid separation means beforebeing delivered into the middle pressure portion of the compressor.
 6. Arefrigerator, comprising: a refrigerating cycle device including acompressor, a radiator connected to a discharge side of the compressor,decompression means connected to an exit side of the radiator, and aheat absorber into which the liquid refrigerant discharged from thedecompression means flows, and which is filled with a carbon dioxiderefrigerant; an outer case; an inner case; and a heat insulatingmaterial for filling a gap between the outer case and the inner case;wherein a high pressure refrigerant pipe extending from the radiator isembedded in the heat insulating material.
 7. The refrigerator accordingto claim 6, wherein: a second heat insulating material which has lowerthermal conductivity than the heat insulating material is provided inthe heat insulating material arranged in a back of the refrigerator; andthe high pressure refrigerant pipe is placed outside a side edge of thesecond heat insulating material.